continental margin contraction in the late Meramecian to early Chesterian and is not clearly associated with the Antler orogeny.

Fryer, P., Wheat, C.G., Williams, T., Kelley, C., Johnson, K., Ryan, J., Kurz, W., Shervais, J., Albers, E., Bekins, B., Debret, B., Deng, J., Dong, Y., Eickenbusch, P., Frery, E., Ichiyama, Y., Johnston, R., Kevorkian, R., Magalhaes, V., Mantovanelli, S., Menapace, W., Menzies, C., Michibayashi, K., Moyer, C., Mullane, K., Park, J.-W., Price, R., Sissmann, O., Suzuki, S., Takai, K., Walter, B., Zhang, R., Amon, D., Glickson, D., Pomponi, S., 2020. Mariana serpentinite mud volcanism exhumes subducted seamount materials: implications for the origin of life. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 378, 20180425.

https://doi.org/10.1098/rsta.2018.0425 The subduction of seamounts and ridge features at convergent plate boundaries plays an important role in the deformation of the overriding plate and influences geochemical cycling and associated biological processes. Active serpentinization of forearc mantle and serpentinite mud volcanism on the Mariana forearc (between the trench and active volcanic arc) provides windows on subduction processes. Here, we present (1) the fi rst observation of an extensive exposure of an undeformed Cretaceous seamount currently being subducted at the Mariana Trench inner slope; (2) vertical deformation of the forearc region related to subduction of Pacific Plate seamounts and thickened crust; (3) recovered Ocean Drilling Program and International Ocean Discovery Program cores of serpentinite mudflows that confirm exhumation of various Pacific Plate lithologies, including subducted reef limestone; (4) petrologic, geochemical and paleontological data from the cores that show that Pacific Plate seamount exhumation covers greater spatial and temporal extents; (5) the inference that microbial communities associated with serpentinite mud volcanism may also be exhumed from the subducted plate seafloor and/or seamounts; and (6) the implications for effects of these processes with regard to evolution of life.

Fu, L., Li, D., Mi, T., Zhao, J., Liu, C., Sun, C., Zhen, Y., 2020. Characteristics of the archaeal and bacterial in situ communities in core sediments from Southern Yap Trench via sampling by the manned submersible Jiaolong . Science of The Total Environment 703, 134884.

http://www.sciencedirect.com/science/article/pii/S0048969719348764 The hadal environment is the deepest part of the ocean and harbors a significant number of unique microbial communities. Here, we collected core sediment samples of Southern Yap Trench with the deep-sea manned Jiaolong submersible and analyzed the microbial community structure and abundance in the samples through high-throughput sequencing and real-time fluorescence quantitative PCR (qPCR), taking physicochemical parameters into account to explore potential environmental drivers and metabolic pathways therein. Considering the typical 'V - shape' topography and frequent sediment collapses on trench walls, the core sediments of Southern Yap Trench harbored distinct microbial populations with fluctuating distributions and metabolic processes dominated by Proteobacteria and Thaumarchaeota. To discover the main potential metabolic processes of microbes, functional genes were detected by qPCR. The abundance of bacteria was greater than that of archaea in Southern Yap Trench sediments. The abundance of ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), sulfate-reducing bacteria (SRB) and denitrifying bacteria (denitrifier) decreased with increasing depth and decreasing total organic carbon (TOC%) and total nitrogen (TN%) and P P showed a positive and significant correlation with TOC% ( <0.01), TN% ( < 0.01), TOC/TN molar ratio P P (C/N ratio) ( < 0.01) and median grain size ( < 0.01). From the perspective of function based on the 16S rRNA gene, aerobic ammonium oxidization, carbon assimilation, and chemoheterotrophic function may be the dominant processes in Southern Yap Trench sediments. Moreover, considering the isolated geomorphological and hydrological characteristics of Southern Yap Trench, we hypothesized that the distinct hadal microbial ecosystem was driven by the endogenous recycling of organic matter in the hadal sediments associated with the trench geomorphology.